Reducing workpiece thickness

ABSTRACT

A method of and apparatus for reducing the thickness of (or skiving) regions of sheet material workpieces, e.g. shoe upper components, involves feeding a workpiece 14 to a band knife (4) and, in advance of said knife, applying pressure to the workpiece 14, using a row of pressure-applying elements (18) to deform a region of the workpiece in relation to the cutting plane (20) of the knife. By controlling the elements (18) to operate in successive sequences of combinations, regions of the workpiece (14) are successively skived as the workpiece (14) passes the knife (4). The operation of the elements (18) is controlled by a computer (CPU), having a memory in which workpiece information data, relating to certain workpiece parameters, as well as in accordance with shape, positional and orientational data is stored. Such data may be generated using optical recognition workpiece means (100,120,140,160).

BACKGROUND OF THE INVENTION

This invention relates to the treatment of sheet material workpieces toreduce the thickness of selected regions thereof. One instance of suchtreatment is to be found in the manufacture of shoes wherein certainregions, particularly the edges, of shoe upper components are reduced inthickness (or "skived") prior to assembling the shoe upper. Skiving iseffective to reduce bulkiness in the upper and to aid its assembly, andthus to improve the appearance of the finished upper and to avoiddiscomfort of the wearer.

One known method of skiving is described in GB-A-1178960. The methodinvolves supporting a workpiece between an upper and a lower feed rollerwhilst it is fed to a band knife. Sandwiched between the workpiece andthe upper roller is a matrix (hence the method is referred to as "matrixskiving") which carries a relief pattern having raised regionscorresponding to the workpiece regions that are subsequently to bereduced by the band knife. The regions of the workpiece engaged by theraised relief pattern are forced downwards against a compressiblesurface on the lower roller, and consequently below the cutting plane ofthe band knife. Any portion of the workpiece disposed below the cuttingplane is removed by the knife as it is fed therepast, and thus aworkpiece is produced with a pattern of reduced thickness regions thatmatch the raised relief pattern of the matrix.

There are, however, problems associated with this existing method ofmatrix skiving namely that each workpiece and each pattern requires aunique matrix, and the matrix has manually to be registered with theworkpiece prior to sandwiching the workpiece and matrix between the feedrollers, which involves time and effort on the part of the operator thatcan affect output potential. In addition, there is some difficultyinvolved in achieving successful registration of the workpiece andmatrix, and this difficulty enhances the possibility of producinginaccurately skived workpieces.

U.S. Pat. No. 3,538,723 describes an apparatus and method of splittingsheet material workpieces, that is, tanned hides. A support roller hasheightwise adjustable sections that enable differing degrees of supportpressure to be applied across the width of the hide. The potentialvariation in support pressure provides the possibility of compensatingfor the inherent non-uniformity in the thickness of the hide andconsequently prevents excessive compression, which could result in theproduction of a non-uniformly split hide. However, as the processrelates to splitting rather than skiving, the hide is supported in aposition such that the cutting plane of the knife to which the hide isfed lies at all times within the material of the hide.

OBJECT OF THE INVENTION

It is an object of the invention to provide a method of and apparatusfor reducing the thickness of selected regions of workpieces, whereby tomaximise output potential by reducing the operator's workpiecepreparation time and to minimise the occurrence of inaccurately skivedworkpieces, such method and apparatus being adaptable to produce anydesired pattern of reduced thickness regions for any particularworkpiece.

SUMMARY OF THE INVENTION

The present invention thus provides, in one of its several aspects, amethod of treating a sheet material workpiece to reduce the thickness ofa selected region thereof using a band knife, in carrying out whichmethod the workpiece is supported on a support for advancing movementpast a blade portion of the band knife, which blade portion extends, ina cutting plane, transversely of the workpiece feed direction, theworkpiece being deformed in relation to the cutting plane in at leastone region thereof, as it is advanced past the knife, such that aportion of the material in said region is removed by the knife therebyreducing the thickness of the workpiece at said region, wherein thedeformation of the workpiece is effected by a plurality ofpressure-applying elements extending in at least one row, immediately inadvance of the knife, transversely of the workpiece feed direction, eachelement being independently movable between an extended condition, inwhich it applies pressure to a section of the workpiece region to causesaid section to be deformed, and a retracted condition, in which it doesnot apply such pressure, selected combinations of the elements beingsuccessively located in their extended condition in timed relation withthe progressive advancing of the workpiece according to the desiredshape of the selected region whose thickness is to be reduced,characterised in that when pressure is applied as aforesaid to aselected region of the workpiece by the elements the support for theworkpiece yields, thereby allowing the relationship between said regionand the cutting plane, and thus the cutting blade, to be varied.

The invention further provides, in another of its several aspects, anapparatus for the treatment of a sheet material workpiece to reduce thethickness of a selected region thereof, comprising a band knife having ablade portion extending in a cutting plane, workpiece feeding means forsupporting a workpiece to be treated and feeding it past the band knife,the blade portion of which extends transversely of the workpiece feeddirection, a plurality of pressure-applying elements extending in atleast one row, immediately in advance of the knife,transversely of theworkpiece feed direction, each element being independently movablebetween an extended condition, in which it can apply pressure to asection of a workpiece region to cause said section to be deformed inrelation to the cutting plane, and a retracted position, in which itdoes not apply such pressure, actuator means for effecting movement ofeach pressure-applying element into and out of its extended condition,and control means for controlling the operation of the actuator meanswhereby combinations of elements can be caused to be successivelylocated in their extended condition in timed relation with the operationof the workpiece feeding means, characterised in that the workpiecefeeding means comprises a workpiece support which is capable of yieldingunder pressure applied by the elements, thereby allowing therelationship between said workpiece region supported thereby and thecutting plane, and thus the cutting blade portion, to be varied.

In carrying out the method in accordance with the invention,furthermore, preferably "upstream" of the pressure-applying elements theworkpiece is supported with both upper and lower surfaces thereofdisposed at one side of the cutting plane, deformation of the region ofthe workpiece causing the material at said region to be deformed acrossthe cutting plane, whereby at least a portion thereof is removed as itmoves past the band knife.

It will thus be appreciated that using the apparatus in accordance withthe invention, in carrying out a method in accordance with theinvention, workpieces can be skived without the need for a dedicatedmatrix, but rather the pressure-applying elements can be controlledautomatically to produce any of a range of skive patterns for any of arange of workpieces; the control of the elements is dynamic to theextent that different sequences of combinations of elements can belocated in their extended condition according to the particularworkpiece and according to the skive pattern to be produced. Renderingthe control of the elements automatic means that an operator need onlythen concern himself/herself with placing workpieces to be skived on theworkpiece feeding means. Moreover, by arranging the workpiece in its"undeformed" condition with both surfaces thereof disposed at one sideof the cutting plane, only the selected regions, which undergodeformation, are skived in the operation of the apparatus.

Preferably in carrying out the method in accordance with the inventionthe movement of the pressure-applying elements is controlled by computercontrol means in accordance with a programmed instruction containingpattern data relating to the desired shape of the selected region. Moreparticularly, the programmed instruction conveniently contains patterndata relating to the succession of combinations of pressure-applyingelements to be located in their extended condition.

In one embodiment of the invention, furthermore, the workpiece shape isidentified by optical workpiece recognition means, which also identifiesthe position and orientation of the workpiece, and the data contained inthe programmed instruction relates to the pattern of the selectedregion, said data being modified according to the position andorientation of the workpiece as identified by the workpiece recognitionmeans, and the movement of the pressure-applying elements beingcontrolled in accordance with such modified data.

More particularly, in said embodiment the optical workpiece recognitionmeans is operative to scan a workpiece to be treated and to generatesignals and supply them to the computer control means according tocertain parameters of the workpiece. In such a case, moreover, thecomputer control means preferably comprises processor means forprocessing such signals to provide workpiece data relating to saidcertain parameters of the workpiece and also workpiece positional andorientational data, and a memory for storing comparison data relating topreviously scanned workpieces, pattern data relating to selected regionsof such workpieces the thickness of which regions is to be reduced, andassignment data associating comparison data for a particular workpiecewith pattern data for a particular selected region, the arrangementbeing such that when a workpiece has been scanned by the workpiecerecognition means the processor means compares the workpiece data withthe comparison data and, upon finding a match, selects the associatedpattern data, and then modifies the pattern data in accordance with theworkpiece positional and orientational data, and the processor meanssupplies control signals to the actuator means in accordance with thethus modified data.

By using computer control means in this manner, it will be appreciated,the control of the pressure-applying elements can be rapidlyimplemented, in timed relation with the operation of the workpiece feedmeans, in order to bring the selected region accurately and reliably tothe blade portion of the band knife. Moreover, by the use of the opticalworkpiece recognition means the operator may load the workpiece on tothe workpiece feed means in any random position and/or orientation andthe workpiece will be "recognised" as to its identity as well as itsposition and orientation and the pattern data will then be modifiedaccordingly and the whole skiving operation be implemented without anyinterference from the operator.

The actuator means may comprise a plurality of actuators, one associatedwith each pressure-applying element, each such actuator having its owndrive arrangement; for example, each actuator may be piezoelectricallydriven. Piezoelectric actuators have the advantage of being relativelysmall so that they can be accommodated in the relatively narrow spacesavailable if the pressure-applying elements are to be sufficientlyclosely arranged with one another to provide adequate resolution of theskived pattern.

Alternatively, the actuator means may comprise a single actuator devicewhich operates through an appropriate linkage or the like, such linkageor the like being selectively engageable with the pressure-applyingelements again under the control of the computer control means.

Where individual actuators are provided, conveniently the deformation ofthe workpiece section engaged by a given pressure-applying element, andthus the amount of material removed at said section by the knife, isdetermined according to the amount of the pressure applied by theactuator; that is to say, by varying the pressure applied by theactuator (which in the case of a piezoelectric actuator is a function ofthe power supplied to it) the amount of deformation can be thuscontrolled.

In one embodiment of the invention the workpiece feeding means comprisesa reach of a conveyor band an upper, workpiece-supporting, surface ofwhich lies in the cutting plane, but which is capable of yielding underpressure applied by the pressure-applying elements and thus being urgedout of said plane. In such an arrangement, furthermore, a further beltmay be provided which is advanced synchronously with the conveyer bandand between which and the conveyer band a workpiece can be held and thusbe fed progressively towards the knife, the pressure-applying elementsapplying pressure to sections of the workpiece through said belt. By theprovision of such a further belt, any tendency of the pressure-applyingelements to drag the workpiece out of position on the workpiece feedingmeans can be avoided. Moreover, preferably the surfaces of the belt andthe workpiece feeding means contacting the workpiece have a relativelyhigh coefficient of friction while the surface of the belt contacted bythe elements has a relatively low coefficient of friction. In this waythe accuracy of the feeding of the workpiece can be enhanced.

There now follows a detailed description, to be read with reference tothe accompanying drawings, of three apparatuses, together with theirmethods of use, in accordance with the invention. It will be understoodthat these apparatuses and their methods of use have been selected fordescription merely by way of non-limiting example of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a first apparatus in accordance with theinvention;

FIG. 2 is a plan view of the apparatus shown in FIG. 1;

FIG. 3 is a side view of the apparatus shown in FIG. 1;

FIG. 4 is a fragmentary view, on an enlarged scale, illustrating theaction of one of the pressure-applying elements of the apparatus shownin FIG. 1;

FIG. 5 is a fragmentary view, taken at right angles to that of FIG. 4,illustrating the action of a plurality of pressure-applying elements ofthe apparatus shown in FIG. 1;

FIG. 6 is an underneath plan view of a workpiece which has been skivedusing the apparatus shown in FIG. 1;

FIG. 7 is a cross-sectional view of the workpiece shown in FIG. 6, takenalong the line VII--VII;

FIG. 8 is a side view of a second apparatus in accordance with theinvention, comprising optical workpiece recognition means; and

FIG. 9 is a side view of a third apparatus in accordance with theinvention comprising workpiece feeding means in the form of two opposedbands.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Shown in FIGS. 1, 2 and 3, in schematic form, is a first apparatus inaccordance with the invention having a band knife 4 supported by a knifeholder 2 adjacent one end of an upper reach of a continuous conveyerband 8 which runs around a conveyer drive roller 10 and an idler roller12. A workpiece 14, typically a footwear component, is supported by theupper reach of the conveyer band 8. The conveyer band 8 is driven by amotor (not shown) through the drive roller 10 so as to feed thesupported workpiece 14 towards the knife 4, i.e. right to left as viewedin FIGS. 1 to 3. The knife 4 is supported with a blade portion 6 thereofpositioned just outwardly of the location at which the conveyer band 8begins to conform to the curvature of the drive roller 10. Theheightwise position of the knife 4 can be adjusted in order that acutting plane 20 passing through the blade 6 lies coincident with, orjust below, the plane of an upper surface of the upper reach of theconveyer band 8, such that the workpiece 14, when supported by saidsurface is supported with its lower surface (and therefore both itslower and upper surfaces) disposed above the cutting plane (20).

Arranged above the conveyer band 8 (by an arrangement not shown) just inadvance (in terms of workpiece feed direction) of the blade 6, is aplurality of pressure-applying elements, in the form of pins 18,arranged in a row and protruding downwards towards the conveyer band 8.(It is to be understood that in other apparatus in accordance with theinvention the pins may be arranged in a plurality of rows extendingtransversely of the workpiece feed direction.) The row extends overapprox. 30 mm long, with the pins 18 spaced 2 mm apart, and is aligned,transversely of, more particularly perpendicularly to, the workpiecefeed direction. Each pin 18 is independently movable between an extendedcondition, in which it is extended towards the cutting plane of theblade 6, and a retracted condition (shown in FIGS. 1 to 3), in which itis retracted away from a plane level with the upper surface of thesupported workpiece 14. To this end, each pin 18 has an individualactuator 16 (not shown individually, but rather as a unit accommodatedtogether in a housing therefor). The actuators are piezoelectricallydriven; a piezoelectric effect is utilised to operate a mechanical lever(not shown) that acts upon the pin. Also associated with each pin 18 isa brake (not shown) which holds the actuator in the position to which itis driven by the actuator. The brake is released during movement of thepin between its extended and retracted conditions.

In using the first apparatus in carrying out a first method inaccordance with the invention, when any one of the pins 18 is located inits extended condition, a section of a workpiece 14 engaged thereby isdeformed into a condition in which the upper and lower surfaces thereofbecome disposed one at each side of the cutting plane 20, that is to saythe cutting plane 20 passes through the body of the material at saidsection, with a result that as the section is moved past the blade 6 aportion is skived therefrom. To this end, as can be seen from the FIG.4, the conveyer band 8 is compressible and indeed compresses under theapplication of pressure by one or more pins 18.

FIG. 4 shows how, as the workpiece 14 passes underneath one of the pins18 in its extended condition, pressure is applied locally to the sectionof the workpiece 14 thus engaged, whereby the workpiece is deformed inrelation to the cutting plane 20 at said section. It will be appreciatedthat if the workpiece 14 is considered to be divided widthwise into aseries of sections, each pin 18 is only capable of applying pressurelocally to one of the sections at any one time. The number of sectionsinto which the workpiece can be considered to be divided is obviouslydependent upon the number and spacing of the pins. Consequently,increased accuracy of skiving can be achieved by increasing the numberof and reducing the spacing between the pins, so as to heighten theresolving power of the apparatus.

FIG. 4 also illustrates that by reason of the proximity of the pins 18to the blade 6 the application of pressure to a workpiece section inadvance of the blade 6 results in a layer 24 being skived from the lowersurface of the workpiece "downstream" of the pin 38 (in the workpiecefeed direction). In comparison, those sections of the workpiece 14 whichpass underneath a pin 18 which is in its retracted condition remainundeformed, with both upper and lower surfaces thereof above the cuttingplane 20, so that no layer is skived from those workpiece sections.

A region, made up of a plurality of adjacent sections, can be skivedfrom the workpiece 14 by bringing those pins 18 which correspond to thesections in combination into their extended condition at the appropriatetime as the region passes underneath the row of pins 18. The combinationof pins must of course be located in their extended condition in timedrelation with the feeding of the workpiece 14 to ensure that theselected region thereof is skived. Moreover, it will be appreciated, asthe shape of the region transversely of the feed direction changes,different combinations of pins 18 will be correspondingly selected.Where a pin is included in two different combinations it may remain incontact with the workpiece; alternatively each combination may beretracted as a unit and the new combination then be brought into itsextended condition.

FIG. 5 shows a combination (A to D) of pins 18 in their extendedcondition at a particular juncture in the feeding of the workpiece 14under the pins 18, thereby deforming a selected, in this case central,region 22 of the workpiece 14 into a condition in which the upper andlower surfaces of the workpiece in the region 22 are disposed one ateach side of the cutting plane 20. The result of this deformation isthat the thickness of the region 22 is reduced by the cutting action ofthe knife.

The depth by which the workpiece 14 is reduced in thickness at theregion 22 is dependent upon the amount of pressure applied by the pins18. Consequently, the degree of reduction in thickness can becontrolled, through the control of the actuators 16, by varying thepressure, and hence by varying the amount of the deformation of theworkpiece region or sections thereof. It follows that the pins do notassume a pre-set height in relation to the conveyer band 8 when in theirextended condition.

The operation of the pins 18 is so timed in relation to the feeding ofthe workpiece 14 that whilst the portion X of the workpiece (FIG. 6) ispassing underneath the row of pins 18, all the pins 18 are in theirretracted condition. As the region Y passes underneath the row of pins18, the combination of pins A to D (as shown in FIG. 5) are brought intotheir extended condition so as to apply pressure to the region 22 of theworkpiece 14 that is to be skived. As the portion Z of the workpiecepasses under the pins 18, the pins 18 are again retracted. The result ofskiving the workpiece 14 is, as shown in FIG. 7, to produce a region 26of reduced thickness.

The actuation of the pins 18 is controlled by computer control meanscomprising a computer CPU which has a memory for storing data relatingto a range of workpiece shapes and pattern data relating to patterns ofreduced thickness regions. In carrying out the first method inaccordance with the invention the operator first identifies to thecomputer CPU e.g. through a keyboard (not shown), the particularworkpiece shape and the selected pattern of reduced thickness regions.The computer CPU would then retrieve from its memory the correspondingdata, in the form of a programmed instruction. Thereafter with theworkpiece 14 placed on to the conveyer band 8 in a desired orientation(as expected by the computer CPU) the workpiece 14 is fed past the rowof pins 18, and the pins 18 are operated in response to control signalsgenerated by the computer programmed instruction and supplied to theactuators 16, so that successive combinations of pins 18 are located intheir extended condition as the workpiece 14 passes therebeneath.

A second apparatus in accordance with the invention is illustratedschematically in FIG. 8, like parts to those shown in earlier Figuresbearing the same reference numerals. Optical workpiece recognition meansis located at a workpiece recognition station generally designated W.The optical workpiece recognition means, which is generally similar inconstruction and operation, except as hereinafter described, to thesystem described in EP-A-0 269 287, comprises, in addition to theconveyer band 8, a conveyer band 180 arranged with an upper reachthereof at the same height as the upper reach of the conveyer band 8 andspaced therefrom by a narrow gap 120 of a size which can be bridged bythe workpiece 14. The conveyer bands 8, 180 operate at the same feedspeed, to feed the workpiece 14 towards the pins 18. Aligned with thegap 120, beneath the conveyer bands 8, 180, is an array of filamentlamps 100, while disposed in opposed relationship with the lamps 100,above the upper reaches of the conveyers, is a camera comprising anarray of light detectors 140 arranged to receive light emitted by thelamps 100 and a high resolution lens 160 which focusses the light on tothe detectors 140. It will be appreciated that the optical paths of thelight from the lamps 100 will be interrupted upon the passage of theworkpiece 14 across the gap 120, the advancing movement of the workpiece14 being progressive, whereby the workpiece is "scanned" by the camera140,160 as it is fed.

The computer CPU of this apparatus comprises processor means wherebyfirstly the signals from the camera are processed to provide workpiecedata relating to certain parameters of the workpiece, together withworkpiece positional and orientational data. In addition, as in the caseof the first apparatus, the computer memory stores data relating to aplurality of workpiece shapes, but in this case such data is used by theprocessor means as comparison data for comparing the workpiece datatherewith thus to identify the scanned workpiece and to determine itsposition and orientation. Moreover a pattern of reduced thicknessregions can also be assigned, using the computer, to each workpiece forwhich comparison data is stored, by storing appropriate assignment datain the computer memory, the pattern data corresponding to the assignedpattern being then capable of recall when a workpiece is recognised asaforesaid.

In using the second apparatus, in carrying out a second method inaccordance with the invention, a workpiece 14 placed by the operator, inrandom position and orientation, on the conveyer 180 is advanced therebyacross the gap 120 on to the upper reach of the conveyer band 8, thecamera 140,160 being effective to scan the workpiece 14 as it crossesthe gap 120 and thereby identify it by comparing the workpiece datarelating to the workpiece with the comparison data stored in thecomputer memory. In addition positional and orientational data for theparticular workpiece is also generated and the assigned pattern datarecalled. The processor means of the computer then modifies the patterndata in accordance with the workpiece positional and orientational dataand, as the workpiece is then fed past the knife 4, a sequence ofcontrol signals, constituting operating instructions, is delivered tothe actuators in accordance with the thus modified pattern data.

A third apparatus in accordance with the invention is shown in FIG. 9.In this apparatus a belt 28 is provided which cooperates with theconveyer band 8 to reduce, if not eliminate, any tendency for thefrictional effects of the pins 18 acting directly on to the surface ofthe workpiece 14 to drag the workpiece 14 out of position as it is beingfed to the knife 6. More particularly, in this apparatus the belt 28 isinterposed between the pins 18 and the workpiece 14, thus to applypressure to the workpiece 14 through the belt, with the workpiece 14thus being sandwiched between the conveyer band 8 and the belt 28. Thebelt 28 runs around three rollers 30, 32 and 34, one of which 32 isdriven synchronously with the conveyer band 8.

In using the third apparatus, in carrying out a third method inaccordance with the invention, the belt 28 bears down on the workpiece14 to ensure that the position of the workpiece 14 relative to themoving surface of the conveyer band is held constant. The pins 18, whenin their extended condition, apply a downwards force to the uppersurface of a lower reach of the belt 28 and the force is thentransmitted through the belt 28 to the workpiece 14, consequentlydeforming the workpiece 14 into the required position, as describedearlier, in which to achieve a reduction in thickness. The upper surfaceof the conveyer band 8 has a "non-slip" coating which tends to hold theworkpiece 14 in one place. The under-surface of the belt 28 similarlyhas a "non-slip" coating with a high coefficient of friction, whereasthe opposite surface of the belt 28 has a much lower coefficient offriction so as to minimise frictional drag when the pins 18 are pressedinto contact therewith.

It will of course be appreciated that the optical workpiece recognitionmeans of the second apparatus could also be incorporated in this thirdapparatus.

We claim:
 1. Apparatus for the treatment of a sheet material workpieceto reduce the thickness of a selected region thereof, comprising:a bandknife (4) having a blade portion (6) extending in a cutting plane (20);workpiece feeding means (8,10,12) for supporting a workpiece (14) to betreated, said feed means being arranged to feed said workpiece past theband knife in a workpiece feed direction, said blade portion extendingtransversely of the workpiece feed direction; a plurality ofpressure-applying elements (18) extending in at least one row,immediately in advance of the knife and transversely of the workpiecefeed direction, each element being independently movable between anextended condition, where it applies pressure to a section of aworkpiece region to cause said section to be deformed in relation to thecutting plane and a retracted position where it does not apply suchpressure; actuator means (16) for effecting movement of eachpressure-applying element (18) into and out of its extended condition;and, control means for controlling the operation of the actuator meanswhereby combinations of elements can be caused to be successivelylocated in their extended condition in timed relation with the operationof the workpiece feeding means; characterised in that the workpiecefeeding means (8, 10, 12) comprises a workpiece support (8) configuredto yield under pressure applied by the elements (18) to vary therelationship between said workpiece region supported thereby and thecutting plane, and thus the cutting blade portion (6), to be varied. 2.Apparatus according to claim 1 characterised in that the control meansis constituted by computer control means operable in accordance with aprogrammed instruction containing pattern data relating to thesuccession of combinations of pressure-applying elements (18) to belocated in their extended condition.
 3. Apparatus according to claim 2characterised in that optical workpiece recognition means(100,120,140,160) is provided by which a workpiece (14) to be treated isscanned and signals are generated and supplied to the computer controlmeans according to certain parameters of the workpiece, and in that thecomputer control means comprisesprocessor means for processing suchsignals to provide workpiece data relating to said certain parameters ofthe workpiece and also workpiece positional and orientational data, anda memory for storing comparison data relating to previously scannedworkpieces, pattern data relating to selected regions of such workpiecesthe thickness of which regions is to be reduced, and assignment dataassociating comparison data for a particular workpiece with pattern datafor a particular selected region, and in that when a workpiece (14) hasbeen scanned by the workpiece recognition means the processor meanscompares the workpiece data with the comparison data and, upon finding amatch, selects the associated pattern data, and then modifies thepattern data in accordance with the workpiece positional andorientational data, and in that the processor means supplies controlsignals to the actuator means (16) in accordance with the thus modifieddata.
 4. Apparatus according to claim 1 characterised in that theworkpiece feeding means (8,10,12) comprises a reach of a conveyor band(8) an upper, workpiece-supporting, surface of which lies in the cuttingplane (20), but which is capable of yielding under pressure applied bythe pressure-applying elements (18) and thus being urged out of saidplane.
 5. Apparatus according to claim 4 characterised by a further belt(28) which is advanced synchronously with the conveyer band (8) andbetween which and the conveyer band a workpiece (14) can be held andthus be fed progressively towards the knife, and characterised in thatthe pressure-applying elements (18) apply pressure to sections of theworkpiece through said belt.
 6. Method of treating a sheet materialworkpiece to reduce the thickness of a selected region thereof using aband knife, the method including the steps of:(a) supporting a workpiece(14) on a support (8) to facilitate movement past a blade portion (6) ofthe band knife (6) on a workpiece movement direction; (b) orienting saidblade portion (6) in a cutting plane (20) which is traverse of theworkpiece movement direction; (c) deforming at least one region of saidworkpiece in relation to the cutting plane as it is moved past the bladeportion (6) in the workpiece movement direction; (d) removing a portionof said workpiece by said band knife; (e) varying the deforming withregard to distinct regions of said workpiece as effected in step (c) andallowing the support provided by said support (8) in step (a) to yieldto variable degrees in order to alter the relationship between saidrespective distinct regions and the cutting plane and thus the cuttingblade (8).
 7. Method as claimed in claim 6 wherein the steps (c) and (e)are performed upstream of the band knife so said workpiece is deformedin accordance with steps (c) and (e) across the cutting plane and soremove at least a portion of the workpiece as it is moved past the bandknife.
 8. Method as claimed in claim 6 wherein prior to performance ofsaid method, a computer-control means is programmed with a sequentialorder for the operations defined in steps (c) and (e) and, said steps(c) and (e) are retrieved from said computer-control means in asequential order to perform said method.
 9. Method as claimed in claim 8wherein prior to performance of the method, the workpiece is identifiedand its position and/or orientation determined and after said positionand/or orientation determination, the sequential order and performanceof steps (c) and (e) held in the computer-control means is modified.